Numerous valves utilize a valve seat in their structure. Many of these structures have a valve structure that, typically, descends to seat upon the valve seat. Where there is a pressure differential between the area “upstream” of the valve seat and the area “downstream” of the valve seat, the energy of the system may be dissipated in undesirable ways. For example, cavitations and/or vibrations can occur, particularly at the moment the valve closes. These occurrences are often reflected in noise at the valve or its associated fixture or upstream/downstream due to vibrations traveling throughout the system. In liquid systems, the vibrations are sometimes caused by pressure waves traveling in the piping system that supplies the valve including what is commonly called water hammer. At other times the cause of the vibrations is more local due to gas trapped in the liquid providing an unstable dynamic system that tends to vibrate at certain flow conditions.
One particular type of valve that can exhibit “noise” problems is a flushometer, commonly used with water closets and urinals. Two particular types of flushometers are well known: diaphragm flushometers and piston flushometers. Diaphragm-type flushometers are exemplified by the flush valve shown in U.S. Pat. No. 6,616,119, which is hereby incorporated herein by reference. Piston-type flushometers are also known, as exemplified by the flush valve shown in U.S. Pat. No. 4,261,545, which is hereby incorporated herein by reference.
A flushometer or faucet valve includes a body 10 with an inlet 12 and outlet 14, a valve assembly 15 with a valve seat 26, a valve member 17 movable in the body 10 toward or away from the valve seat 26 to control flow from the inlet 12 to the outlet 14. The valve assembly 15 has a pressure chamber 50 acting on one side of the valve member 17 opposing the inlet pressure on the other side of the valve member 17. A bypass 40 connects the chamber 50 with the water inlet side. Pressure in the chamber 50 maintains the piston 80 or diaphragm 18 seated to the valve seat 26 and the valve assembly 15 in the closed position. There is a relief valve 30, which may be a mechanical relief valve stem 32 or a solenoid 99 (FIG. 3A) driven, that vents the chamber 50 to the outlet 14 side of the valve to permit the piston 80 or diaphragm 18 to move away from the valve seat 26 and open and control the water flow thru the valve. The piston 80 or diaphragm 18 may have a portion 89/48 to keep it concentric to the valve seat 26 and in axial alignment with the valve seat 26. The valve typically has a refill head 47 or similar flow control device on the outlet side of the diaphragm 18 or piston 80 to confine the path of flow. Valves of this kind are taught in prior art for example in U.S. Pat. Nos. 5,881,993; 5,887,848; 5,213,305; 5,244,179; 6,182,689; 6,260,576; 5,332,192 5,967,182.
It is well known, that in certain environmental and flow conditions, flushometers, such as those discussed above, can start to vibrate and cause noticeable and sometimes undesirable noise. Valve noise in the above described type of valves can be generated thru various mechanisms. If the pressure in some areas falls below vapor pressure due to the Bernoulli Effect, cavitation can occur, which can cause violent oscillations and forces on the valve. Air may become trapped or present in the air chamber, such as due to a high level of gas dissolved in the water from the inlet. Air entrapped in the pressure chamber 50 can introduce a different impedance, due to the variance in compression of the mixed air/water fluid compared to only water, of the piston/diaphragm and pressure chamber 50 and therefore make the flow unsteady. In addition, the piping upstream or downstream of the valve can cause undesirable oscillations in the valve.
This noise can also be described as flutter or water hammer. Numerous attempts have been made to address such noise. Some valves as described in U.S. Pat. No. 4,248,270 employ a resilient flow control device that deflects or deforms under the inlet pressure, and therefore dynamically controls the flow rate. U.S. Pat. No. 6,616,119 employs a diaphragm that has a molded rubber skirt on the inlet side of the flush valve which deforms with pressure and controls the flow. The skirt attempts to dampen vibration with “friction” tabs. The disadvantage of the resilient member often is that the modulus of elasticity of such members rapidly changes with temperature. It therefore makes it difficult to control the flow rates consistently over different operating temperatures due to the tabs' (of the '119 patent) friction against the outer diameter of the barrel.
Another means to control noise is to introduce friction between the moving diaphragm or piston and the valve housing. For example, U.S. Pat. No. 5,865,420 diaphragm teaches a refill head 47 on the outlet side of the valve which introduces friction between the housing and the moving refill head, therefore damping vibrations. The aforementioned refill head 47 on the inlet side also touches the housing barrel to introduce friction.
Some valves, e.g. U.S. Pat. No. 4,040,440 employ sound absorbing treatment on the outlet side, or generate turbulence as taught in U.S. Pat. No. 4,967,998. Some flushometer designs have grooves in the outlet skirt as well (made of plastic or metal) to control the flow as well. Other cage type valves employ perforated and grooved members, plugs and skirts as a means to make the flow turbulent to reduce noise throughout the flush cycle as shown in U.S. Pat. No. 4,024,891 or 3,990,475. However, the limited stroke of the chamber controlled valves does not allow for elaborate absorption treatment or perforation of members. In addition, the difficulty of those perforated and grooved members shown in prior art, is that even though they suppress noise thru the introduction of turbulence, they severely restrict flow thru the valve when the valve is in an open position or opening/closing stroke. In other configurations, the geometry adds friction or flow resistance to the opening or closing stroke. This cannot be adopted in valves that have a smaller stroke and larger flow rate requirements.
Further complicating matters, some of the portion of the noise/hammer occurs at the moment before the closing of the valve is completed. The Bernoulli effect is especially strong at that moment, as the inlet pressure builds up to static pressure of a typical residential or commercial water supply line, while at the same time the pressure on the outlet dramatically reduces (typical to atmospheric pressure). Present mechanisms at the outlet side of the valve seat have only little effect at that moment.